The Fall Out Boy member and his longtime girlfriend Meagan Camper are expecting a baby in the New Year.

"Happy New Year! We're kicking the year off with news of the best gift yet," he shared with his 1.5 million Instagram followers. "[Baby] coming to our family in 2018... love Pete, Meagan, Bronx and Saint."

The pair, who began dating in 2011, is proud parents to 3-year-old Saint. Pete also shares Bronx with ex-wife Ashlee Simpson Ross.

In the announcement, Saint had the honor of holding up a pink box causing fans to believe the sex of the upcoming family member is a girl.

Photos

While his kids are still on the younger side, Pete previously revealed to Elle that his oldest son was showing an interest in music. At the same time, he loved the fact that Bronx saw him as dad first and foremost.

"My [then] six year old comes out on the road, and he's endlessly curious about everything: 'Where is there ice under the arena?' For him, it's like being at your dad's office," Pete explained to the publication. "There's a picture of us playing for 40,000 people in Los Angeles, and there's a picture of my son on the side of the stage playing his Nintendo DS. I'm just his dad. It's such a cool relationship to have."

As for his longtime partner Meagan, Pete is the first to share how much she's impacted his life for the better.

"She is a person that puts up with my madness," he once told Howard Stern. "I'm a man in love! Not jumping on the couch, but..."